SCP-XXXX-2 should be stored in a hat box, lined with class 2 electromagnetic shielding, in an separate locker

"a separate locker"

Under no circumstances, including testing, should instances of SCP-XXXX-1 be moved away more than 500 meters

I think "be moved more than 500 meters away" is better phrasing.

Testing is only permitted in rooms no larger than 10 meters by 10 meters or more than one instance of SCP-XXXX-1 without the authorization of Dr. Sanders or the Site Director, and should only occur using D-class subjects.

You've got three disparate topics in one sentence here, and it's a little confusing. Suggest "Testing is permitted only in rooms no larger than 10 by 10 meters. Multiple instances of SCP-XXXX-1 may not be tested together without the authorization of Dr. Sanders or the Site Director. All testing must be carried out with D-class subjects."

Instances of SCP-XXXX-1 superficially appear to be standard security headsets, outside of a small label with consecutive serial number and the marking 'Prometheus Labs' in relief on the back of the main unit, and there is no apparent power source or port to access the internal workings of the unit.

I think "There is no apparent power source or port to access the internal workings of the unit" should be a separate sentence. I would also suggest replacing "apparent power source" with "power connector" (see below).

There is no apparent power source. Examination via oscilloscope have confirmed that the crystal circuit is not this source.

The first sentence here seems redundant, since you use the exact same phrase in the main body of the description just above. I understand what you mean — that there's no plug on the outside for a power source, and nothing like a battery inside. That's why I suggested saying "There is no power connector or port" above.

Wearers of SCP-XXXX-1 will launch themselves far quicker than they should be capable, and through obstacles.

Suggest "Wearers of SCP-XXXX-1 will move far faster than they should be able to, and will also break through obstacles where present."

Despite extensive testing, no upper limit for speed has been found nor any obstacle capable of stopping a wearer of SCP-XXXX-1 from placing themselves between the projectile and the wearer of SCP-XXXX-2.

This one's tricky. "Despite extensive testing, no upper limit for speed has been found, and no obstacle has stopped a wearer of SCP-XXXX-1 from placing themselves between the projectile and the wearer of SCP-XXXX-2."

Wearers of SCP-XXXX-1 appear to travel at speeds in excess of .7c, and through meter-thick of reinforced concrete.

"Wearers of SCP-XXXX-1 appear to travel at speeds in excess of .7c, and are able to pass through up to a meter of reinforced concrete."

Many of our customers are people in sensitive positions, with powerful enemies, face internal tension in their own organization, or some combination of the three.

"Many of our customers are in sensitive positions, have powerful enemies, face internal tension in their own organizations, or some combination of the three."

(Incidentally, this whole PL grant request should be in a quote block.)

If this could be compelled from a given bodyguard to do this, and guarantee their safety - that's a very significant relief from some very powerful people with deep pockets.

"If a given bodyguard could be compelled to do this, thus guaranteeing the client's safety, that would be a very significant relief for some very powerful people with deep pockets."

Personal, short-distance relativistic travel from [REDACTED] and the recovered, albeit cryptic and incomplete information on psychic 'radar' recovered from GRU Division "P", could be combined into a man-portable protective system.

"Recovered" twice in one sentence. I think you could fix this by picking a different adjective for the first instance — perhaps "workable" would be appropriate. "Workable, albeit cryptic and incomplete" implies (to me) that it does function, but by no means perfectly.

Least of all, such technology could be used to protected our own personnel.

I think you want "last of all" there (protecting their own personnel may indeed be the thing they're least concerned about, but that's not really how "least of all" is used).

Observers note that, based on D-1711's actions after landing on the grenade, diving onto the grenade was involuntary.

I think "the dive was involuntary" is less redundant but still gets the point across. And I'm giggling again.

Mechanically fired anti-material rifle

For military weaponry, it's "anti-materiel." (An anti-material rifle would probably be a skip on its own.)

The slug liquefied D-2776

Jumped into past tense for a second. Should be "liquefies." I'm giggling again. I am a terrible person.

Research Assistant ██████████ three other observing researchers all requested class A amnesiacs and transfer to a different project.

Needs an "and" after the blackbox. Also, this is a really quibbly thing, but nowadays site readers prefer the term "amnestics" (since "amnesiac" already means "person with amnesia").

Identical to Test A-6, except AM rifle replaced with standard service rifle, and a sheet of plywood 25mm thick.

This one needs another sentence to explain where the plywood is. Something like "Identical to Test A-6, except AM rifle replaced with standard service rifle. D-3740 is separated from D-4509 by a sheet of plywood 25mm thick."

D-7837 suffers injuries expected when hitting steel in excess of ████ m/s, and died on impact, but his corpse successfully stops the bullet.

That past tense again. I would suggest replacing "and died on impact" with "dying on impact."

The "results" section for tests B-2 and B-3 is the same. B-3's test result needs to be edited to reflect the use of concrete.

D-5562 passes through D-10355 successfully stopping the bullet.

Needs a comma after "D-10355." This thing is getting worse all the time. I don't suppose it would be that hard to go around a person, but I guess they didn't bother providing for that.

Thanks, I guess the horrible grammar mistakes are just what happens when I write when I'm tired.
I made a few edits in other places, mostly to fix inconsistency in operation. Think this should go to the main wiki?

Examination via oscilloscope have confirmed that the crystal circuit is not this source.

"Has confirmed."

Wearers of SCP-XXXX-1 will move far faster than they should be able to, and through obstacles.Despite extensive testing

Missing a space after the period there.

In Test XXXX-A-1, everything's in past tense. I know it's the baseline test, but I think the parameters and results should still be in present tense like the other tests. Tests XXXX-D-4 and D-5-1 also have past tense in the results section that should be changed to present tense.

Once you get those things cleared up, yes, I think it's ready for the main site!